Pediatrics is known as a new modern medicine in the society today.[1]Hippocrates, Aristotle, Celsus, Soranus, and Galen, understood the differences in growing and maturing organisms that necessitated different treatment: Ex toto non sic pueri ut viri curari debent ( "In general, boys should not be treated in the same way as men."Celsus[2]).[1]

A second century AD manuscript by the Greek physician and gynecologist Soranus of Ephesus dealt with neonatal pediatrics.[6] Byzantine physicians Oribasius, Aëtius of Amida, Alexander Trallianus, and Paulus Aegineta contributed to the field.[1] The Byzantines also built brephotrophia (crêches).[1] Islamic writers served as a bridge for Greco-Roman and Byzantine medicine and added ideas of their own, especially Haly Abbas, Serapion, Avicenna, and Averroes. The Persian scholar and doctor al-Razi (865–925) published a short treatise on diseases among children.[7] The first book about pediatrics was Libellus [Opusculum] de aegritudinibus et remediis infantium 1472 ("Little Book on Children Diseases and Treatment"), by the Italian pediatrician Paolo Bagellardo.[8] In sequence came Bartholomäus Metlinger's Ein Regiment der Jungerkinder 1473, Cornelius Roelans (1450-1525) no title Buchlein, or Latin compendium, 1483, and Heinrich von Louffenburg (1391-1460) Versehung des Leibs written in 1429 (published 1491), together form the Pediatric Incunabula, four great medical treatises on children's physiology and pathology.[1]

The Swedish physician Nils Rosén von Rosenstein (1706–1773) is considered to be the founder of modern pediatrics as a medical specialty,[9][10] while his work The diseases of children, and their remedies (1764) is considered to be "the first modern textbook on the subject".[11] Pediatrics as a specialized field of medicine continued to develop in the mid-19th century; Abraham Jacobi (1830–1919) is known as the father of pediatrics in the USA because of his many contributions to the field.[12] He was born in Germany, where he received his medical training, but later practiced in New York City.

The first generally accepted pediatric hospital is the Hôpital des Enfants Malades (French: Hospital for Sick Children), which opened in Paris in June 1802 on the site of a previous orphanage.[13] From its beginning, this famous hospital accepted patients up to the age of fifteen years,[14] and it continues to this day as the pediatric division of the Necker-Enfants Malades Hospital, created in 1920 by merging with the physically contiguous Necker Hospital, founded in 1778.

The body size differences are paralleled by maturation changes. The smaller body of an infant or neonate is substantially different physiologically from that of an adult. Congenital defects, genetic variance, and developmental issues are of greater concern to pediatricians than they often are to adult physicians. A common adage is that children are not simply "little adults". The clinician must take into account the immature physiology of the infant or child when considering symptoms, prescribing medications, and diagnosing illnesses.

A major difference between the practice of pediatric and adult medicine is that children, in most jurisdictions and with certain exceptions, cannot make decisions for themselves. The issues of guardianship, privacy, legal responsibility and informed consent must always be considered in every pediatric procedure. Pediatricians often have to treat the parents and sometimes, the family, rather than just the child. Adolescents are in their own legal class, having rights to their own health care decisions in certain circumstances. The concept of legal consent combined with the non-legal consent (assent) of the child when considering treatment options, especially in the face of conditions with poor prognosis or complicated and painful procedures/surgeries, means the pediatrician must take in to account the desires of many people, not just the patient.

The training of pediatricians varies considerably across the world. Depending on jurisdiction and university, a medical degree course may be either undergraduate-entry or graduate-entry. The former commonly takes five or six years, and has been usual in the Commonwealth. Entrants to graduate-entry courses (as in the US), usually lasting four or five years, have previously completed a three- or four-year university degree, commonly but by no means always in sciences. Medical graduates hold a degree specific to the country and university in and from which they graduated. This degree qualifies that medical practitioner to become licensed or registered under the laws of that particular country, and sometimes of several countries, subject to requirements for "internship" or "conditional registration".

Pediatricians must undertake further training in their chosen field. This may take from four to eleven or more years, (depending on jurisdiction and the degree of specialization). The post-graduate training for a primary care physician, including primary care pediatricians, is generally not as lengthy as for a hospital-based medical specialist.

In the United States, a medical school graduate wishing to specialize in pediatrics must undergo a three-year residency composed of outpatient, inpatient, surgical, and critical care rotations. Specialties within pediatrics require further training in the form of 2-3 year fellowships. Specialties include critical care, gastroenterology, neurology, infectious disease, hematology/oncology, rheumatology, pulmonology, child abuse, emergency medicine, endocrinology, neonatology, and others.[17]

In most jurisdictions, entry-level degrees are common to all branches of the medical profession, but in some jurisdictions, specialization in pediatrics may begin before completion of this degree. In some jurisdictions, pediatric training is begun immediately following completion of entry-level training. In other jurisdictions, junior medical doctors must undertake generalist (unstreamed) training for a number of years before commencing pediatric (or any other) specialization. Specialist training is often largely under the control of pediatric organizations (see below) rather than universities,and depending on jurisdiction.